Low-lift pallet truck



Jan. 14, 1969 G. M. DUGELAY 3,421,775

LOW-LIFT PALLET TRUCK Filed Feb. e. 1967 United States Patent O 3,421,775 LOW-LIFT PALLET TRUCK George Michel Dugelay, ChatenayMalabry, France, assignor to Saxby, Paris, France, a corporation of France Filed Feb. 6, 1967, Ser. No. 614,157 Claims priority, applicatior; France, Feb. 23, 1966, 5 8

U.S. Cl. 280-43.12 1 Claim Int. Cl. B62b 3/00 ABSTRACT 0F THE DISCLOSURE The present invention -relates to small handling machines of the type commonly referred to as low-lift pallet trucks, these machines being frequently provided with fork arms which are intended to be inserted beneath loads, pallets or skids for the purpose of lifting them slightly and displacing them rover short distances.

Low-lift pallet trucks of known types generally cornprise a frame having two longitudinal members or fork arms which are fitted at one end with casters and joined together at the other end by a bridge, said bridge being supported on an elevating unit which is carried by a guide-wheel axle.

The lifting action is performed by means of a link-rod system ycomprising a lifting cross-shaft which is rotatably mounted at each end on the truck frame and on each side of which are keyed respectively a top lever and a bottom lever, the end of said top lever being pivoted about a pin carried by the guide-wheel axle and the end of said bottom lever being pivotally coupled to one end of a transmission link-rod extending along the corresponding longitudinal member whilst the other end of said transmission rod is adapted to actuate a system for lifting and lowering casters relatively to the truck frame, with the result that the longitudinal members `are lifted on the casters when the elevating unit lifts the bridge from the guide-wheel axle.

The `aim of this invention is to provide an improvement to the above-described lift mechanism, the primary object of which is to simplify the manufacture of said mechanism and to facilitate the application of the system to low-lift pallet trucks of different Widths.

The improvement according to the invention essentially consists in providing the lifting cross-shaft with a constant noncircular cross-section along its entire useful length between the end bearings and in mounting the top and bottom levers of the link-rod system by forcibly fitting the ends of said levers over said non-circular cross-section.

As Ia consequence, keys are no longer required and a free lchoice is permit-ted in the positions 0f said levers along the length of the lifting cross-shaft, with the result that the assembly can readily be adapted to the width of the corresponding elements of the pallet truck. These advantages in turn permit of simplification in both machining and I:assembly and therefore a reduction in cost price without in any way affecting the ruggedness of the mechanism as a whole.

One form of execution of the invention is shown 3,421,775 Patented Jan. 14, 1969 ICC by way of example in the accompanying drawings, in which:

FIG. l is a simplified view in side elevation of a lowlift pallet truck;

FIG. 2 is a plan view of the link-rod system; and

FIG. 3 is a detail view on a larger scale, this view being taken in cross-section along the line III-III of FIG. 2.

The low-lift pallet truck is mainly of conventional design. It comprises a frame with two longitudinal members or fork arms 1 which are supported at one end on casters 2 and joined together at the other end by a bridge 3 which is supported on an elevating unit 4, said elevating unit being carried on a guide-Wheel axle 5.

The elevating unit 4 is constituted by a jack which is supplied from a pump actuated by a draw-bar 6. The bridge 3 is supported by a pivot-pin 7 on the jack of the elevating unit 4.

The link-rod system `comprises a lifting cross-shaft 8 which, in accordance with the invention, has a hexagonal cross-section and is rotatably mounted at each end in bearing-bushes 9 which are rigidly fixed to the frame. There are fitted on each side of said cross-shaft 8 a top lever or pitman 10 and a bottom lever or pitman 11 which are provided for this purpose with terminal openings of `corresponding cross-sectional configuration. The end of each upper lever 10 is pivoted on a pin 12 carried by one end of a cross-member 13 which is supported by the axle 5 by means of a thrust-bearing which permits the pivotal motion of said axle and of the elevating unit 4 with respect to said cross-member 13 as initiated by the operating handle 16. The end of each bottom lever 11 is pivotally `coupled to one end of a transmission link-rod 14 which extends along the corresponding fork larm 1. The other end of said transmission link-rod is pivotally coupled to one end 15a of an elbowed lever 15 and a fork-arm caster 2 is -rotatably mounted at the other end 15b of said elb owed lever 15 which is pivoted on a spindle 16, said spindle being in turn rotatably mounted on the fork arm.

It is already known that, when the jack of the elevating mechanism 4 lifts the bridge 3 and is supported on the guide-wheel axle 5, it initiates the simultaneous pivotal motion of the top levers 10 and bottom levers 11 on the one hand and of the elbowed levers 15 on the other hand, the pivotal motion of the top and bottom levers being transmitted to the elbowed levers by the link-rod 14, with the result that the frame as a whole moves upwards parallel to itself.

The novelty of this invention lies in the structural design of the lifting cross-shaft 8 and of the levers 10 and 11 which are forcibly fitted on said cross-shaft, thereby securing the advantages which have been set forth in the introductory part of this specification.

It will be readily yapparent that both the lifting shaft and lever end-passages can be endowed with a noncircular cross-sectional configuration other than hexagonal and that any detail modifications can be contempalted without thereby departing either from the Scope or the spirit of the invention.

What I claim is:

1. In a low-lift pallet truck having a frame with two laterally spaced, longitudinally extending lifting members and a bridge xedly connected between said lifting members adjacent one end thereof, casters mounted on said lifting members adjacent the other end thereof, a guidewheel axle connected to said frame land having a guide wheel thereon for supporting the bridge end of said truck,

means and said casters for raising the other end of said truck in response to raising of the bridge end of the truck, said linkage means including pivot shaft means mounted on said frame adjacent each of said lifting members and a pair of first lever members positioned on the opposite sides of said truck adjacent said laterally spaced lifting members with one end of each of said rst lever members being interconnected to said elevating means and the other end of each of said first lever membe-rs being nonlrotatably secured to said pivot shaft means, said linkage means further including a pair of second lever members positioned on the opposite sides of said truck adjacent said laterally spaced lifting members with one end of each of said second lever members being nonrotatably secured to said pivot shaft means, a pair of intermediate rods connected between the other end of said pair of second lever members and said casters, and arm means pivotally mounting said casters on said lifting members with said arm means being pivotally connected to said rod members, the improvement wherein said pivot shaft means comprises a single cross-shaft extending between said laterally spaced lifting members with the opposite ends of said cross-shaft being pivotally connected to said pair of lifting members, the portion of said cross-shaft extending between said lifting members having a uniform noncircular cross section and the ends of said pairs of first and second lever members having noncircular openings substantially identical in size and shape to the cross-section of said `cross shaft for nonrotatably securing said pairs of first and second lever members to said cross-shaft.

References Cited UNITED STATES PATENTS 1,891,658 12/1932 Thomas 74-548 3,188,107 6/1965 Quayle 2SC-43.12 3,188,698 6/1965 Zoll et al 74-519 BENJAMIN HERSH, Primary Examiner.

ROBERT R. SONG, Assistant Examiner. 

